1. Field of Invention
The invention relates to an ink-jet head for printing by ejecting ink onto a record medium, to a method for manufacturing the ink-jet head, and to an ink-jet printer having the ink-jet head.
2. Description of Related Art
In an ink-jet printer, an ink-jet head distributes ink, which is supplied from an ink tank, to pressure chambers. The ink-jet head selectively applies pulse pressure to each pressure chamber to eject ink through a nozzle connected with each pressure chamber. As a means for selectively applying pulse pressure to the pressure chambers, an actuator unit or the like may be used in which ceramic piezoelectric sheets are laminated. The printing operations are carried out while reciprocating such a head at a high speed in the widthwise direction of paper.
In the ink-jet head of the related art, a pressure chamber and an ink passage are formed by subjecting the piezoelectric ceramics to a cutting operation with a diamond cutter. Individual electrodes or driving electrodes made of a metallic film are formed over the actuator units corresponding to the individual pressure chambers. On the surface of the ink passage on the lower side of the pressure chamber, there is disposed a nozzle plate, which is made of a synthetic resin film and has a number of ink ejection ports.
However, the manufacturing costs for the aforementioned ink-jet head of the related art is high because the head main body is made of piezoelectric ceramics. The manufacturing costs is further raised by the cutting operation which uses the diamond cutter.
As a solution for the aforementioned cost problems, there is known an inkjet head constructed such that a passage unit, having one-dimensionally arranged pressure chambers and ink passages made of relatively inexpensive and easily workable metal plates, and an actuator unit, using a continuous flat plate layer of piezoelectric ceramics spanning across the pressure chambers, are fixed on each other. If the passage unit is constructed by inexpensive metal plates, the cost for the material can be suppressed. Moreover, the manufacturing costs can also be suppressed by using metal plates, because metal plates are more workable than piezoelectric ceramics and can be finely lightened at many points by etching them.
Here, for fixing different materials of the metal and the piezoelectric ceramics, it is preferable to use a room temperature setting adhesive for easy bonding operations. In order to obtain a sufficient adhesion strength and resistance, however, a heat setting adhesive has to be used to bond the two materials in a heated state. Since there is a large difference in the linear expansion coefficient between the metal and the piezoelectric ceramics, when they are bonded in the heated state, the passage unit having a larger linear expansion coefficient shrinks more than the actuator unit, in a facial direction, when returned to the room temperature. Therefore, the ink-jet head warps and is convex toward the actuator unit. This warp causes poor printing and deterioration in a production yield.